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Nutrition mainstay to success

Q. Could you provide an update on protein-losing enteropathies (PLE) dietary therapy for dogs?

A. Dr. Debra L. Zoran at the 2007 American College of Veterinary Internal Medicine Forum in Seattle lectured on dietary therapy of PLE and severe inflammatory bowel disease (IBD) in dogs. Some relevant points are provided here.

Primary causes of protein-losing enteropathies

Protein-losing enteropathies (PLE) are a spectrum of diseases occurring primarily in dogs that manifest in non-specific protein loss through the gastrointestinal tract. Although commonly called an enteropathy, the protein loss can occur through the stomach, small intestine or large intestine.

Protein-losing enteropathies can be primary (e.g., genetic or heritable disorders such as those that occur in Soft-Coated Wheaton Terriers or Basenjis) or secondary to another problem. From the lists of common diseases associated with protein-losing enteropathies in dogs (p.11S), particularly of note are any of the gastroenterides, lymphangiectasia and IBD. Therapy of these diseases should be aimed at treatment of the primary problem, but nutritional therapy is an essential aspect of success.

Inflammatory bowel disease (IBD)

First, remember that there are many causes of GI inflammation. Just finding lymphocytes and plasma cells or eosinophils on an intestinal biopsy does not confirm IBD, which is a chronic, idiopathic disease of the intestinal tract that has no identifiable cause.

In addition to finding inflammatory infiltrates in the GI mucosa, thorough elimination of the other causes of intestinal inflammation (e.g., dietary intolerance/allergy, bacterial enteritis) is warranted. Because a diagnosis of IBD is a concession that only symptomatic therapy remains, the long-term prognosis is more guarded than if a diagnosis and specific therapy are known.

Finally, if a specific treatment can be employed, avoidance of high doses of anti-inflammatory or immunosuppressive drugs (with substantial short-and long-term side effects), or at least the use of smaller doses for a shorter time, may be possible.

Lymphocytic plasmacytic enteritis (LPE) is primarily a disease of middle-aged to older dogs, and is uncommonly seen in young dogs. It is well-known that the gut is a massive immune organ — responding to a large number and variety of foods, bacteria, parasites and other antigens every day. Therefore, it is not surprising that the response to exposure to some of these antigens is increased numbers of lymphocytes and plasma cells, or even other cell types such as eosinophils.

At this time, it is impossible to distinguish the primary cause of these inflammatory infiltrates in the gut wall. Thus, appropriately performed food trials to eliminate adverse reactions to foods as the cause of the infiltrate are essential. An appropriate food trial may require at least six to eight weeks to achieve reversal of signs. It takes two to three weeks for the body to remove old antigens and more time is necessary for the body to resolve the inflammatory lesions. It is reasonable to use anti-inflammatory doses of prednisone during this time, but the dose should be tapered over several weeks. Use the diet response to gauge the real effect of the therapy.

Possibly the most difficult and important aspect of conducting a food trial to rule out food allergy as the cause of gut inflammation is the dietary history. Many over-the-counter pet foods contain a wide variety of protein sources, so it can be quite difficult to identify a commercial diet that is truly novel. For this reason, many veterinarians have used hydrolyzed protein diets as their trial diet in the hopes that the hydrolysates will have low immunogenicity.

Unfortunately, making the proteins smaller does not prevent the epitopes that are responsible for activating the immune reaction from being exposed. In fact, in humans, hydrolysates can be even more antigenic in some children, resulting in anaphylaxis and other hypersensitivity reactions. Further refinement of proteins (into elemental amino-acid forms) will be required to completely eliminate this problem. In addition to problems with persistent antigenicity, hydrolyzed protein diets may have changes in taste and digestibility, and as the proteins are hydrolyzed into smaller and smaller forms, the osmolarity of the diets increases, which has been blamed for causing diarrhea in humans and pets.